Short text messages are limited to 170 characters per message and it is important to track the characters in each text. To show SMS character count on iPhone devices and see the number of characters left to reach the limit, do as follows:
1. Open the Settings from the main menu
2. Scroll down to the list of default applications on your iPhone and tap the Messages settings
3. Scroll down to SMS/MMS settings and make sure to toggle on the Character Count option
4. The characters in your text messages is now counted and showed.